Firewall Steering seal/grommet
A common seal/grommet that rots out/fails on the 80 is the steering column firewall seal. Since the section of the steering column that goes through the firewall is unsupported (due to the uni-joint) there's considerable stress applied to the bellows of the seal. Over time it will rip out/disintegrate. Basically a poor design by Mr T.
With winter approaching (eventually - still sunny and warmish in early Jan in the SF Bay area), it seemed a good idea to replace the seal.
The picture below shows what needs to be removed to be able to slide the coupler off and then remove the seal. Rotate the front wheels so they are in the straight ahead position and the steering coupler should line up as in the picture. Loosen off the 12mm bolts/nuts. Also loosen the 12mm bolt that locks the lower shaft (that goes through the firewall) to the coupler. See picture #2 below this one.
Labeled is the velcro strap that holds the padding down to the firewall, the padding can be folded to the right to create an 'inspection' opening to gain access to the two bolts that hold the seal in place (pictures further down).
Once the 2 12mm bolts/nuts have been removed (be sure to have loosened the 12mm bolt on the coupler clamp first, see picture below), you can rotate/swivel/jiggle the uni-joint end of the coupler top plate and swing it out of the way of the coupler.
You can see the 12mm bolt that locks the coupler to the steering shaft that goes through the firewall. The coupler has splines, so put a witness mark (white paint works well) on the coupler and the steering shaft prior to removing the coupler so you can re-align it correctly during assembly. If you don't line it up correctly your steering wheel will be cocked to the left or right when driving straight. The 12mm bolt needs to be FULLY removed to allow the coupler to slide off the shaft - it is only sitting in place on the picture below to show what the bolt looks like and where it goes. With the uni-joint end of the coupler swung out of the way AND the 12mm clamp bolt (below) removed, the coupler will just slide off the steering shaft that goes through the firewall.
With the coupler removed you can then easily remove the 10mm bolts that hold the seal to the firewall. You may need to use a flat head screwdriver to pry the seal off the firewall (may just be stuck a little from the years of being clamped in place), then just slip it off the steering shaft. In the picture you can see some white paint (witness) mark that was placed on the steering shaft to match a similar mark on the coupler clamp.
And here's a picture of the damaged/rotted seal and the new Toyota replacement seal (with part number).
Top & bottom pictures of old seal and new seal for comparison. This side of the seal faces TOWARDS the firewall when you reinstall the new seal.
Installation is just a matter of reversing the steps taken to remove. I applied liberal amounts of dielectric grease to the seal's rubber area to ensure it would slide easily over the steering shaft and to try to keep it lubricated when the shaft rotates while steering.
Install/tighten the 10mm bolts LAST so as to allow the seal to be able to shift/move around while the steering shaft is unsupported while you're bolting the coupler and uni-joint sections back together.